Obesity is most commonly caused by excessive food intake coupled with limited energy expenditure and/or lack of physical exercise. Obesity increases the likelihood of development of various diseases, such as diabetes mellitus, hypertension, atherosclerosis, coronary artery disease, sleep apnea, gout, rheumatism and arthritis. Moreover, mortality risk directly correlates with obesity, such that, for example, a body-mass index in excess of 40 results in an average decreased life expectancy of more than 10 years.
Current pharmacological treatment modalities include appetite suppressors targeting receptor classes (e.g., CB1, 5-HT2C, and NPY); regulators of the appetite circuits in the hypothalamus and the molecular actions of ghrelin; and nutrient-absorption inhibitors targeting lipases. Unfortunately, none of the current modalities has been shown to effectively treat obesity without causing adverse effects, some of which can be very severe.
High blood glucose levels stimulate the secretion of insulin by pancreatic beta-cells. Insulin in turn stimulates the entry of glucose into muscles and adipose cells, leading to the storage of glycogen and triglycerides and to the synthesis of proteins. Activation of insulin receptors on various cell types diminishes circulating glucose levels by increasing glucose uptake and utilization, and by reducing hepatic glucose output. Disruptions within this regulatory network can result in diabetes and associated pathologic syndromes that affect a large and growing percentage of the human population.
Patients who have a glucose metabolism disorder can suffer from hyperglycemia, hyperinsulinemia, and/or glucose intolerance. An example of a disorder that is often associated with the aberrant levels of glucose and/or insulin is insulin resistance, in which liver, fat, and muscle cells lose their ability to respond to normal blood insulin levels.
In view of the prevalence and severity of obesity, diabetes and associated metabolic and non-metabolic disorders, along with the shortcomings of current treatment options, alternative treatment modalities that modulate, for example, appetite, glucose and/or insulin levels and enhance the biological response to fluctuating glucose levels in a patient remain of interest.
In addition, in the pharmaceutical sciences it is frequently beneficial, and sometimes imperative, to improve one of more physical properties of the treatment modality (e.g., a protein, peptide, or hydrophobic molecule) of interest and/or the manner in which it is administered. Improvements of physical properties include, for example, methods of increasing water solubility, bioavailability, serum half-life, and/or therapeutic half-life; modulating immunogenicity and/or biological activity; and/or extending the circulation time. Such improvements must be imparted without adversely impacting the bioactivity of the treatment modality. Thus, it may be advantageous for alternatives to current treatment options for obesity, diabetes and associated metabolic and non-metabolic disorders, to possess one or more improved physical properties.